The broad objective of this project is to gather 24-hour ambulatory blood pressure data on healthy, normotensive men and women (ages 18-34) and to relate these data to blood pressure response to laboratory stressors. Methodological questions include: frequent vs. standard ambulatory recording rates, comparison of different rates of sampling ambulatory pressure using various level and variability indices, day-by-day and year- by-year consistency of ambulatory records, investigation of different methods of quantifying and analyzing pressure level and variability. Substantive questions include: comparison of lab and natural setting blood pressure, differences between men and women in lab and ambulatory responses, relations between family history and blood pressure according to age/sex norms and lab/ambulatory blood pressure in initial and follow-up observations. The lab stressors include; mental arithmetic, video game, cold pressor test, and postural change. Lab measures include: continuous systolic and diastolic pressure, heart rate, skin conductance, and cardiac and flow measures using impedance cardiography. This project should provide "normative" data on blood pressure level and variability relevant to the use of ambulatory monitoring in the assessment of hypertension and in the evaluation of effects of drug and/or behavioral treatments. Results of the methodological studies should also lead to improved methods of acquiring and analyzing ambulatory blood pressure. The research on lab and natural blood pressure and ther cardiovascular processes under different stress conditions and according to several risk factors should provide significant information on the regulation of blood presssure in normotensive individuals and in the development and pathogenesis of hypertension.